For a lot of reasons, I disagree with Kahane. But if the annexation is unequivocal and emphatic, there will be less overtly hostile Arabs, and thus easier to transfer out those who are overtly hostile.
An emigration package could also be offered for those who leave voluntarily, similar to the immigration package offered to Jews who make aliya, and the government can buy up Arab real estate and protect those who sell or facilitate sales from reprisals, including one-way tickets to the country of their choice and new identities.
But every Arab emigrant family member would have to be interviewed separately to determine that they are not being held against their will, are not Jewish, and are leaving of their own volition together with the head of family.
But ultimately there is no secular solution. No secular political program will ever alleviate the problem any more than a secular ethnic Jewish state has solved Jewish problems.
The world thinks the lesson it was supposed to learn from Jewish suffering is the need for massive secularization. This is not what Israel was supposed to teach the nations. Considering the totalistic nature of Halakhah the association of secularism with Jews is really ironic.